Battery cell and preparation method thereof, battery device and power-using device

Abstract

The present application discloses a battery cell and a method for preparing the same, a battery device and an electrical device. The battery cell includes an electrode assembly, the electrode assembly includes a pole piece, the pole piece includes a current collector and an active material layer disposed on at least one side in the thickness direction of the current collector, and a groove is disposed on the surface of the active material layer away from the current collector. The groove includes a plurality of widening portions and a plurality of narrowing portions, and the widening portions and the narrowing portions are alternately disposed along the extension direction of the groove, the width of the widening portion is greater than the width of the narrowing portion, and the depth of the widening portion is greater than the depth of the narrowing portion. The pole piece of this structure is used in the battery cell to improve the charge and discharge rate and cycle life of the battery cell.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery cell and a preparation method thereof, a battery device and an electrical device. Background Art

[0002] With the development of new energy technologies, battery cells are being used more and more widely. Battery cells have high energy density, high reliability, long service life, and are green and environmentally friendly to the social environment. They have been widely used in passenger cars, commercial vehicles, electric bicycles, heavy trucks, energy storage facilities, battery swap stations, engineering manufacturing, intelligent equipment, etc. At the same time, they also promote technology development and research in communication terminals, medical equipment, energy development, etc.

[0003] In battery technology, how to improve the charge and discharge rate and cycle life of battery cells is a technical problem that needs to be solved urgently. Summary of the invention

[0004] The embodiments of the present application provide a battery cell and a method for preparing the same, a battery device and an electrical device, which can effectively improve the charge and discharge rate and cycle life of the battery cell.

[0005] In the first aspect, the embodiment of the present application provides a battery cell, the battery cell includes an electrode assembly, the electrode assembly includes a pole piece, the pole piece includes a current collector and an active material layer disposed on at least one side of the current collector in the thickness direction, and a groove is disposed on the surface of the active material layer away from the current collector. The groove includes a plurality of widening portions and a plurality of narrowing portions, and along the extension direction of the groove, the widening portions and the narrowing portions are alternately disposed, the width of the widening portion is greater than the width of the narrowing portion, and the depth of the widening portion is greater than the depth of the narrowing portion.

[0006] In the above technical solution, the groove includes a plurality of widening parts and a plurality of narrowing parts. The widening parts and the narrowing parts are arranged alternately along the extension direction of the groove. The width of the widening part is greater than the width of the narrowing part, and the depth of the widening part is greater than the depth of the narrowing part. The widening part can be understood as the position where the width and depth of the groove are expanded, and the narrowing part can be understood as the position where the width and depth of the groove are narrowed. By forming grooves on the surface of the active material layer, the pole piece is used in a battery cell. Since the plurality of widening parts and the plurality of narrowing parts are arranged alternately, the widening part is convenient for storing electrolyte, and the electrolyte can be stored more between two adjacent narrowing parts, so that the electrolyte can infiltrate more into the deep position of the active material layer, improve the lithium ion transmission rate at the deep position of the active material layer, and improve the current density at the deep position of the active material layer, thereby improving the charge and discharge rate and cycle life of the battery cell.

[0007] In some embodiments, the width of the groove gradually decreases from the widened portion to the narrowed portion.

[0008] In the above technical solution, the groove width is gradually reduced from the widened portion to the narrowed portion, so that there is a smooth transition between the width of the widened portion and the width of the narrowed portion, and there is no step between the widened portion and the narrowed portion, which is beneficial to alleviate stress concentration and reduce the risk of active material layer falling off.

[0009] In some embodiments, the width of the widened portion is W1, satisfying 10 μm≤W1≤200 μm.

[0010] In the above technical solution, W1≥10μm, the widened part will not be too wide, the groove has a higher capillary action ability, and the infiltration ability of the electrolyte along the extension direction of the groove is improved, especially when the battery cell is placed vertically, the wettability along the top is improved. W1≤200μm, the groove will not be too narrow, which is conducive to more electrolyte storage in the groove. Therefore, W1 is between 10μm and 200μm, which can take into account the capillary action brought by the groove and the ability of the groove to store electrolyte.

[0011] In some embodiments, 90 μm≤W1≤120 μm.

[0012] In the above technical solution, the capillary effect brought by the groove and the ability of the groove to store electrolyte can be further taken into account.

[0013] In some embodiments, the width of the narrowed portion is W2, satisfying 5 μm≤W2≤100 μm.

[0014] In the above technical solution, W2≥5μm, the narrowing portion is not too narrow, and the narrowing portion has a small degree of inhibition on the capillary action of the electrolyte along the extension direction of the groove. W2≤100μm, the narrowing portion is not too wide, and has little effect on the storage of electrolyte in the widening portion. Therefore, 5μm≤W2≤100μm can take into account both the capillary action brought by the groove and the ability of the groove to store electrolyte.

[0015] In some embodiments, 30 μm≤W2≤90 μm.

[0016] In the above technical solution, the capillary effect brought by the groove and the ability of the groove to store electrolyte can be further taken into account.

[0017] In some embodiments, the depth of the groove gradually decreases from the widened portion to the narrowed portion.

[0018] In the above technical solution, the depth of the groove is gradually reduced from the widened portion to the narrowed portion, and there is a smooth transition between the depth of the widened portion and the depth of the narrowed portion. There is no step between the widened portion and the narrowed portion, which is beneficial to alleviate stress concentration and reduce the risk of active material layer falling off.

[0019] In some embodiments, the depth of the widened portion is H, satisfying 5 μm≤H≤300 μm.

[0020] In the above technical solution, when H≥5μm, the groove will not be too shallow, which is conducive to storing more electrolyte in the groove. When H≤300μm, the groove will not be too deep, so when the groove is formed on the surface of the active material layer by the processing equipment, the risk of cutting through the active material layer and damaging the current collector due to processing errors can be reduced, thereby improving the quality of the pole piece. Therefore, the depth of the widened portion is between 5μm and 300μm, which can take into account both the quality of the pole piece and the ability of the groove to store electrolyte.

[0021] In some embodiments, 10 μm ≤ H ≤ 20 μm.

[0022] In the above technical solution, the quality of the electrode and the ability of the groove to store electrolyte can be further taken into consideration.

[0023] In some embodiments, the distance between two adjacent narrowing portions is W3, satisfying 0.02mm≤W3≤20mm.

[0024] In the above technical solution, W3≥0.02mm, the distance between two adjacent narrowing parts will not be too small, which is conducive to storing electrolyte. W3≤20mm, the distance between two adjacent narrowing parts will not be too large, so that each groove can be provided with more widening parts to store electrolyte. Therefore, the distance between two adjacent narrowing parts is between 0.02mm and 20mm, which can take into account the ability of the groove to store electrolyte and the total amount of electrolyte stored in the groove.

[0025] In some embodiments, 1 mm ≤ W3 ≤ 3 mm.

[0026] In the above technical solution, the ability of the groove to store electrolyte and the total amount of electrolyte stored in the groove can be further taken into consideration.

[0027] In some embodiments, the groove extends along a first direction, a plurality of the grooves are provided, and the plurality of the grooves are arranged at intervals along a second direction, the first direction intersects with the second direction, and the first direction and the second direction are both perpendicular to the thickness direction of the current collector.

[0028] In the above technical solution, a plurality of grooves are provided, which can greatly improve the charge and discharge rate and cycle life of the battery cell.

[0029] In some embodiments, along the third direction, the distance between two adjacent grooves is W4, satisfying 0.02 mm ≤ W4 ≤ 10 mm, and the third direction, the first direction, and the thickness direction of the current collector are perpendicular to each other.

[0030] In the above technical solution, W4≥0.02mm, the distance between two adjacent grooves will not be too small, the number of grooves set per unit area will not be too many, and the loss of active material layer caused by the grooves will not be too much, so the impact on the energy density of the battery cell is small. W4≤10mm The distance between two adjacent grooves will not be too large, so a larger number of grooves can be set to improve the wettability of the electrolyte in the active material layer and improve the charge and discharge rate and cycle life of the battery cell. Therefore, the distance between two adjacent grooves is between 0.02mm and 10mm, which can take into account the energy density of the battery cell as well as the charge and discharge rate and cycle life of the battery cell.

[0031] In some embodiments, 1.5 mm ≤ W4 ≤ 5 mm.

[0032] In the above technical solution, the energy density of the battery cell as well as the charge and discharge rate and cycle life of the battery cell can be further taken into consideration.

[0033] In some embodiments, the second direction is the length direction of the current collector, and the first direction is parallel to or at an angle to the width direction of the current collector.

[0034] In the above technical solution, the first direction is parallel to or forms an angle with the width direction of the current collector, and the extension direction of the groove is parallel to or forms an angle with the width direction of the current collector.

[0035] The extension direction of the groove is parallel to the width direction of the current collector, which makes it easy to control the size of the groove and reduces the difficulty of preparing the electrode.

[0036] The extending direction of the groove forms an angle with the width direction of the current collector, and the groove is arranged obliquely, allowing the dimension of the groove along its extending direction to be longer.

[0037] In some embodiments, along the width direction of the current collector, the current collector has a first edge and a second edge relative to each other, and the groove has a first end close to the first edge and a second end close to the second edge; wherein the first end extends to the first edge; and / or the second end extends to the second edge.

[0038] In the above technical solution, the first end extends to the first edge, which can improve the wettability of the electrolyte at the first edge. The second end extends to the second edge, which can improve the wettability of the electrolyte at the second edge.

[0039] In some embodiments, along the width direction of the current collector, the current collector has a first edge and a second edge relative to each other, and the groove has a first end close to the first edge and a second end close to the second edge; wherein the first end is spaced apart from the first edge; and / or the second end is spaced apart from the second edge.

[0040] In the above technical solution, the first end of the groove is spaced apart from the first edge, so that when the groove is formed on the surface of the active material layer by processing equipment, the risk of damaging the collector due to processing errors and the processing stroke exceeding the first edge can be reduced, thereby improving the quality of the pole piece.

[0041] The second end of the groove is spaced apart from the second edge, so that when the groove is formed on the surface of the active material layer by processing equipment, the risk of damaging the collector due to processing errors and the processing stroke exceeding the second edge can be reduced, thereby improving the quality of the pole piece.

[0042] In some embodiments, along the width direction of the current collector, the distance between the first end and the first edge is L1, satisfying 0.5mm≤L1≤3mm; and / or, along the width direction of the current collector, the distance between the second end and the second edge is L2, satisfying 0.5mm≤L2≤3mm.

[0043] L2≥0.5mm, the distance between the groove and the first edge is not too close, so when the groove is formed on the surface of the active material layer by the processing equipment, the risk of damaging the current collector due to processing errors and the processing stroke exceeding the active material layer can be reduced, thereby improving the quality of the pole piece. L2≤3mm, the groove is not too far from the first edge, which is conducive to the preparation of grooves with longer extension dimensions, thereby improving the wettability of the electrolyte in the active material layer and improving the charge and discharge rate and cycle life of the battery cell. Therefore, the distance between the first end and the first edge is between 0.5mm and 3mm, which can take into account the reliability of the battery cell and the charge and discharge rate and cycle life of the battery cell.

[0044] L3≥0.5mm, the distance between the groove and the second edge is not too close, so when the groove is formed on the surface of the active material layer by the processing equipment, the risk of damaging the current collector due to processing errors and the processing stroke exceeding the active material layer can be reduced, thereby improving the quality of the pole piece. L2≤3mm, the groove is not too far from the second edge, which is conducive to the preparation of grooves with longer extension dimensions, thereby improving the wettability of the electrolyte in the active material layer and improving the charge and discharge rate and cycle life of the battery cell. Therefore, the distance between the second end and the second edge is between 0.5mm and 3mm, which can take into account the reliability of the battery cell and the charge and discharge rate and cycle life of the battery cell.

[0045] In some embodiments, 0.6 mm ≤ L1 ≤ 1.5 mm; and / or, 0.6 mm ≤ L2 ≤ 1.5 mm.

[0046] In the above technical solution, 0.6 mm ≤ L1 ≤ 1.5 mm, which can further take into account the reliability of the battery cell and the charge and discharge rate and cycle life of the battery cell.

[0047] 0.6mm≤L2≤1.5mm, which can further take into account the reliability of the battery cell and the charge and discharge rate and cycle life of the battery cell.

[0048] In some embodiments, the electrode plate is a negative electrode plate of the electrode assembly.

[0049] In some embodiments, the grooves are formed by laser etching.

[0050] In the above technical solution, the groove is formed by laser etching, which greatly reduces the difficulty of forming the groove and greatly improves the efficiency of forming the groove.

[0051] In some embodiments, the electrode assembly is a wound structure or a stacked structure.

[0052] In a second aspect, an embodiment of the present application provides an electrical device, which includes the above-mentioned battery device, and the battery device is used to provide electrical energy.

[0053] In a third aspect, an embodiment of the present application provides a method for preparing a battery cell, the method comprising:

[0054] Providing a pole piece, the pole piece comprising a current collector and an active material layer disposed on at least one side of the current collector in a thickness direction;

[0055] A continuous laser with periodically changing power is used to etch grooves with alternating widths and depths on the surface of the active material layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0057] Figure 1 A schematic diagram of the structure of a vehicle according to some embodiments of the present application;

[0058] Figure 2 An exploded schematic diagram of a battery device according to some embodiments of the present application;

[0059] Figure 3 An exploded schematic diagram of a battery cell according to some embodiments of the present application;

[0060] Figure 4 This is a schematic diagram of the structure of the pole pieces of some embodiments of the present application at a certain viewing angle;

[0061] Figure 5This is a schematic diagram of the structure of the pole piece of some embodiments of the present application from another perspective;

[0062] Figure 6 for Figure 5 Enlarged view of part A in the middle;

[0063] Figure 7 for Figure 5 Sectional view along CC;

[0064] Figure 8 for Figure 7 Enlarged view of middle part B;

[0065] Fig. 9 Schematic diagrams of the structures of pole pieces of other embodiments of the present application;

[0066] Fig.10 Schematic diagrams of the structures of pole pieces of some other embodiments of the present application;

[0067] Fig.11 This is a schematic diagram of the structure of the pole pieces of some other embodiments of the present application;

[0068] Fig.12 A schematic diagram of the structure of a laser device according to some embodiments of the present application;

[0069] Fig.13 This is a flow chart of a method for preparing a battery cell according to some embodiments of the present application.

[0070] Icons: 100-battery device; 10-battery cell; 11-end cap; 12-electrode assembly; 13-shell; 20-casing; 21-first casing; 22-second casing; 23-accommodating space; 30-pole piece; 31-current collector; 311-first edge; 312-second edge; 32-active material layer; 33-groove; 331-widening portion; 332-narrowing portion; 333-first end; 334-second end; 1000-vehicle; 200-motor; 300-controller; X-length direction; Y-width direction; Z-thickness direction; S1-first direction; S2-second direction; S3-third direction.

[0071] The drawings are not drawn to scale. DETAILED DESCRIPTION

[0072] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0073] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by technicians in the technical field of this application; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned drawings and any variations thereof are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order or a primary and secondary relationship.

[0074] Reference to "embodiment" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiment may be included in at least one embodiment of the present application. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments.

[0075] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "attached" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0076] The term "and / or" in this application is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this application generally indicates that the associated objects before and after are in an "or" relationship.

[0077] In the embodiments of the present application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width and other dimensions of various components in the embodiments of the present application shown in the drawings, as well as the overall thickness, length, width and other dimensions of the integrated device are only exemplary descriptions and should not constitute any limitation to the present application.

[0078] The term “plurality” used in this application refers to two or more (including two).

[0079] In the embodiment of the present application, the battery cell may be a secondary battery. A secondary battery refers to a battery cell that can be continuously used by activating active materials by charging after the battery cell is discharged.

[0080] Battery cells include, but are not limited to, lithium-ion batteries, sodium-ion batteries, sodium-lithium-ion batteries, lithium metal batteries, sodium metal batteries, lithium-sulfur batteries, magnesium-ion batteries, nickel-hydrogen batteries, nickel-cadmium batteries, lead-acid batteries, and the like.

[0081] A battery cell generally includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charge and discharge process of the battery cell, active ions (such as lithium ions) are embedded and removed between the positive electrode and the negative electrode. The separator is set between the positive electrode and the negative electrode to reduce the risk of short circuit between the positive and negative electrodes, while allowing active ions to pass through.

[0082] In some embodiments, the positive electrode may be a positive electrode sheet, and the positive electrode sheet may include a positive electrode current collector and a positive electrode active material disposed on at least one surface of the positive electrode current collector.

[0083] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material is disposed on either or both of the two facing surfaces of the positive electrode current collector.

[0084] As an example, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum with a silver-plated surface, stainless steel with a silver-plated surface, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel or titanium, etc. may be used. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0085] As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for battery cells may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3Mn 1 / 3O2 (also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 )、LiNi 0.8 Co0.1Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds, etc.

[0086] In some embodiments, the positive electrode may be a foamed metal. The foamed metal may be a nickel foam, a copper foam, an aluminum foam, an alloy foam, etc. When the foamed metal is used as the positive electrode, the positive electrode active material may not be provided on the surface of the foamed metal, but of course, the positive electrode active material may also be provided. As an example, a lithium source material, potassium metal or sodium metal may also be filled or / and deposited in the foamed metal, and the lithium source material is lithium metal and / or a lithium-rich material.

[0087] In some embodiments, the negative electrode may be a negative electrode sheet, and the negative electrode sheet may include a negative electrode current collector.

[0088] As an example, the negative electrode current collector may be a metal foil, a foamed metal or a composite current collector. For example, as the metal foil, aluminum with a silver-plated surface, stainless steel with a silver-plated surface, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel or titanium, etc. may be used. The foamed metal may be foamed nickel, foamed copper, foamed aluminum, foamed alloy, etc. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0089] As an example, the negative electrode sheet may include a negative electrode current collector and a negative electrode active material disposed on at least one surface of the negative electrode current collector.

[0090] As an example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material is disposed on either or both of the two facing surfaces of the negative electrode current collector.

[0091] As an example, the negative electrode active material may adopt the negative electrode active material for battery cells known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for battery cells may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0092] In some embodiments, the material of the positive electrode current collector may be aluminum, and the material of the negative electrode current collector may be copper.

[0093] In some embodiments, the separator is a separator membrane, which can be any known porous separator membrane with good chemical stability and mechanical stability.

[0094] As an example, the material of the separator may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different. The separator may be a separate component located between the positive and negative electrodes, or may be attached to the surface of the positive and negative electrodes.

[0095] In some embodiments, the separator is a solid electrolyte, which is disposed between the positive electrode and the negative electrode and serves to transmit ions and isolate the positive and negative electrodes.

[0096] In some embodiments, the battery cell further includes an electrolyte, which plays a role in conducting ions between the positive and negative electrodes. The electrolyte can be liquid, gel or solid. Among them, the liquid electrolyte includes an electrolyte salt and a solvent.

[0097] In some embodiments, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0098] In some embodiments, solvent can include ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone. Solvent can also be selected ether solvent. Ether solvent can include ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran, diphenyl ether and crown ether One or more.

[0099] Among them, the gel electrolyte includes a skeleton network with a polymer as the electrolyte, combined with an ionic liquid-lithium salt.

[0100] Among them, solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0101] As an example, the polymer solid electrolyte may be polyether (polyethylene oxide), polysiloxane, polycarbonate, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, a single ion polymer, polyionic liquid-lithium salt, cellulose, and the like.

[0102] As an example, the inorganic solid electrolyte may include an oxide solid electrolyte (crystalline perovskite, sodium superconducting ion conductor, garnet, amorphous LiPON film), a sulfide solid electrolyte (crystalline lithium superion conductor (lithium germanium phosphosulfide, silver germanium sulfide), amorphous sulfide) and one or more of a halide solid electrolyte, a nitride solid electrolyte and a hydride solid electrolyte.

[0103] As an example, the composite solid electrolyte is formed by adding an inorganic solid electrolyte filler to a polymer solid electrolyte.

[0104] In some embodiments, the electrode assembly is a wound structure, wherein the positive electrode sheet and the negative electrode sheet are wound into a wound structure.

[0105] In some embodiments, the electrode assembly is a laminate structure.

[0106] As an example, a plurality of positive electrode sheets and a plurality of negative electrode sheets may be provided respectively, and the plurality of positive electrode sheets and the plurality of negative electrode sheets may be alternately stacked.

[0107] As an example, a plurality of positive electrode sheets may be provided, and the negative electrode sheet is folded to form a plurality of stacked folded segments, with a positive electrode sheet sandwiched between adjacent folded segments.

[0108] As an example, both the positive electrode sheet and the negative electrode sheet are folded to form a plurality of stacked folded sections.

[0109] As an example, a plurality of separators may be provided, each of which is provided between any adjacent positive electrode sheets or negative electrode sheets.

[0110] As an example, the separator may be disposed continuously, and may be disposed between any adjacent positive electrode sheets or negative electrode sheets by folding or winding.

[0111] In some embodiments, the shape of the electrode assembly can be cylindrical, flat, or polygonal.

[0112] In some embodiments, the electrode assembly is provided with tabs, which can lead current out of the electrode assembly. The tabs include a positive tab and a negative tab.

[0113] In some embodiments, the battery cell may include a housing. The housing is used to encapsulate components such as the electrode assembly and the electrolyte. The housing may be a steel housing, an aluminum housing, a plastic housing (such as polypropylene), a composite metal housing (such as a copper-aluminum composite housing), or an aluminum-plastic film.

[0114] As an example, the battery cell may be a cylindrical battery cell, a prismatic battery cell, a soft-pack battery cell or a battery cell of other shapes. The prismatic battery cell includes a square-shell battery cell, a blade-shaped battery cell, a polygonal battery cell, such as a hexagonal battery cell.

[0115] The battery apparatus mentioned in the embodiments of the present application may include one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly may include multiple battery cells, which are connected in series, in parallel or in mixed connection through a busbar.

[0116] In some embodiments, a battery cell assembly is generally formed by arranging a plurality of battery cells; as an example, the battery cell assembly may be a battery module, which is formed by arranging and fixing a plurality of battery cells to form an independent module.

[0117] As an example, a battery module may be formed by bundling a plurality of battery cells by cable ties.

[0118] In some embodiments, the battery device may be a battery pack, which may include a case and one or more battery cell assemblies, wherein the battery cell assemblies are accommodated in the case.

[0119] As an example, the battery cell assembly may be a battery module, and the battery cell assembly may be accommodated in the box by fixing the battery module in the box.

[0120] As an example, the battery cell assembly may also be housed in the case by directly fixing a plurality of battery cells to the case.

[0121] As an example, the box may include a first box and a second box. The first box and the second box are buckled together to form a closed space inside the box to accommodate the battery cell assembly. The closed here means covered or closed, which can be sealed or unsealed. The first box can be a top cover or a bottom plate.

[0122] As an example, the box body may include a top cover, a frame and a bottom plate. The top cover and the bottom plate are respectively connected to the frame, so that a closed space is formed inside the box body to accommodate the battery cell assembly.

[0123] As an example, the box body can be used as a part of the chassis structure of the vehicle. For example, the top cover of the box body can become at least a part of the floor of the vehicle, or the frame of the box body can become at least a part of the cross beam and longitudinal beam of the vehicle.

[0124] In some embodiments, the battery device refers to an energy storage device, which includes a box body, at least one side of which is provided with a door. The energy storage device includes an energy storage container, an energy storage cabinet, and the like.

[0125] The development of battery technology must take into account many design factors at the same time, such as energy density, cycle life, discharge capacity, charge and discharge rate and other performance parameters. In addition, battery safety must also be considered.

[0126] In battery technology, in order to obtain high energy density, the thickness of the active material layer on the electrode is generally designed to be thicker, and the compaction density of the active material layer is also larger, which creates resistance to the infiltration of the electrolyte, especially from the surface of the active material layer to the deep layer (the active material layer is close to the current collector). The infiltration resistance gradually increases, the wettability of the electrolyte in the active material layer gradually decreases, the ion transmission rate gradually decreases, and the current density gradually decreases, affecting the charge and discharge rate and cycle life of the battery cell.

[0127] In view of this, in order to solve the problem that the deep resistance of the active material layer increases, resulting in a decrease in the battery charge and discharge rate and cycle life. The embodiment of the present application provides a battery cell, the battery cell includes an electrode assembly, the electrode assembly includes a pole piece, the pole piece includes a current collector and an active material layer arranged on at least one side of the current collector in the thickness direction, a groove is formed on the surface of the active material layer, the groove includes a plurality of widening parts and a plurality of narrowing parts, along the extension direction of the groove, the widening parts and the narrowing parts are alternately arranged, and the width of the widening part is greater than the width of the narrowing part.

[0128] The widening portion can be understood as the position where the groove width is widened, and the narrowing portion can be understood as the position where the groove width is narrowed. By forming grooves on the surface of the active material layer, the grooves can improve the capillary action of the active material layer and improve the wettability of the electrolyte in the active material layer. The pole piece is used in a battery cell. Since multiple widening portions and multiple narrowing portions are alternately arranged, the widening portion is convenient for storing electrolyte, and the electrolyte can be stored more between two adjacent narrowing portions, so that the electrolyte can infiltrate more into the deep position of the active material layer, improve the lithium ion transmission rate in the deep position of the active material layer, and improve the current density in the deep position of the active material layer, thereby improving the charge and discharge rate and cycle life of the battery cell.

[0129] The technical solutions described in the embodiments of the present application are applicable to various electrical devices using battery cells and battery devices, such as mobile phones, portable devices, laptop computers, electric vehicles, electric toys, electric tools, vehicles, ships and spacecraft, for example, spacecraft include airplanes, rockets, space shuttles and spacecraft, etc.

[0130] For the convenience of description, the following embodiments are described by taking the electric device as a vehicle as an example.

[0131] Please refer to Figure 1 , Figure 1 The schematic diagram of the structure of the vehicle 1000 provided in some embodiments of the present application. The vehicle 1000 is provided with a battery device 100 inside, and the battery device 100 can be provided at the bottom, head or tail of the vehicle 1000. The battery device 100 can be used to power the vehicle 1000, for example, the battery device 100 can be used as an operating power source of the vehicle 1000.

[0132] The vehicle 1000 may further include a controller 300 and a motor 200 , wherein the controller 300 is used to control the battery device 100 to supply power to the motor 200 , for example, to meet the power requirements of starting, navigating, and driving the vehicle 1000 .

[0133] In some embodiments of the present application, the battery device 100 can not only serve as an operating power source for the vehicle 1000, but also serve as a driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0134] Please refer to Figure 2 , Figure 2 This is a schematic exploded view of a battery device 100 according to some embodiments of the present application. The battery device 100 may include a box body 20 and a battery cell 10 . The box body 20 is used to accommodate the battery cell 10 .

[0135] Among them, a closed space for accommodating the battery cell 10 is formed inside the box 20. The box 20 can adopt a variety of structures. In some embodiments, the box 20 may include a first box 21 and a second box 22, and the first box 21 and the second box 22 are buckled with each other. The first box 21 and the second box 22 can be in various shapes, such as a cuboid, a cylinder, etc. The first box 21 can be a hollow structure with one side open, and the second box 22 can also be a hollow structure with one side open. The open side of the second box 22 is buckled with the open side of the first box 21 to form a box 20 with a closed space. It is also possible that the first box 21 is a hollow structure with one side open, and the second box 22 is a plate-like structure. The second box 22 is buckled on the open side of the first box 21, so as to form a box 20 with a accommodating space 23.

[0136] In the battery device 100, there may be one or more battery cells 10. If there are more than one battery cell 10, the battery cells 10 may be connected in series, in parallel, or in a mixed connection. A mixed connection means that the battery cells 10 are both connected in series and in parallel. The battery modules may be formed by connecting the battery cells 10 in series, in parallel, or in a mixed connection, and then the battery modules are formed into a whole by connecting the battery cells in series, in parallel, or in a mixed connection, and then accommodated in the box 20. Alternatively, all the battery cells 10 may be directly connected in series, in parallel, or in a mixed connection, and then the whole formed by all the battery cells 10 is accommodated in the box 20.

[0137] In some embodiments, the battery device 100 may further include a busbar component (not shown in the figure), and multiple battery cells 10 may be electrically connected through the busbar component to achieve series connection, parallel connection, or mixed connection of multiple battery cells 10. The busbar component may be a metal conductor, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc.

[0138] Please refer to Figure 3 , Figure 3 This is a schematic diagram of an exploded view of a battery cell 10 according to some embodiments of the present application. The battery cell 10 may include a housing 13 , an electrode assembly 12 , an end cover 11 and other functional components.

[0139] The shell 13 is a component for accommodating the electrode assembly 12. The shell 13 can be a hollow structure with an opening at one end, or a hollow structure with openings at both ends. The shell 13 can be made of a variety of materials, such as copper, iron, aluminum, steel, aluminum alloy, etc. The shell 13 can be in a variety of shapes, such as a cylinder, a cuboid, etc. For example, in Figure 3 In the embodiment, the housing 13 is a rectangular parallelepiped.

[0140] In some embodiments, the electrode assembly 12 includes a positive electrode sheet 30 and a negative electrode sheet 30 , and the positive electrode sheet 30 and the negative electrode sheet 30 are wound to form the electrode assembly 12 .

[0141] In some embodiments, an isolation member may be further provided between the positive electrode sheet 30 and the negative electrode sheet 30 .

[0142] The end cap 11 is a component that covers the opening of the shell 13 to isolate the internal environment of the battery cell 10 from the external environment. The end cap 11 covers the opening of the shell 13, and the end cap 11 and the shell 13 together define a sealed space for accommodating the electrode assembly 12, the electrolyte and other functional components. The shape of the end cap 11 can be adapted to the shape of the shell 13. For example, the shell 13 is a rectangular parallelepiped structure, and the end cap 11 is a rectangular plate structure adapted to the shell 13. For another example, the shell 13 is a cylindrical structure, and the end cap 11 is a circular plate structure adapted to the shell 13. The material of the end cap 11 can also be a variety of materials. For example, the end cap 11 can be a metal material, such as copper, iron, aluminum, steel, aluminum alloy, etc. The material of the end cap 11 can be the same as or different from the material of the shell 13.

[0143] In the battery cell 10, there can be one or two end caps 11. If the shell 13 is a hollow structure with an opening at one end, one end cap 11 is provided accordingly; if the shell 13 is a hollow structure with openings at both ends, two end caps 11 are provided accordingly, and the two end caps 11 cover the two openings of the shell 13 respectively.

[0144] The embodiment of the present application provides a pole piece 30 , which is used in a battery cell 10 to improve the charge and discharge rate and cycle life of the battery cell 10 . The specific structure of the pole piece 30 is described in detail below with reference to the accompanying drawings.

[0145] Figure 4 It is a schematic structural diagram of the pole piece 30 in some embodiments of the present application at a certain viewing angle; Figure 5 It is a schematic structural diagram of the pole piece 30 in some embodiments of the present application from another viewing angle; Figure 6 for Figure 5 Enlarged view of part A in the middle; Figure 7 for Figure 5 Sectional view along CC; Figure 8 for Figure 7 Enlarged view of middle part B; Fig. 9 It is a schematic structural diagram of the pole piece 30 of some other embodiments of the present application; Fig.10 Schematic diagram of the structure of the pole piece 30 of some other embodiments of the present application.

[0146] Reference Figures 4 to 10The embodiment of the present application provides a battery cell 10, the battery cell 10 includes an electrode assembly 12, the electrode assembly 12 includes a pole piece 30, the pole piece 30 includes a current collector 31 and an active material layer 32 disposed on at least one side of the current collector 31 in the thickness direction Z, and a groove 33 is disposed on the surface of the active material layer 32 away from the current collector 31. The groove 33 includes a plurality of widening portions 331 and a plurality of narrowing portions 332, and along the extension direction of the groove 33, the widening portions 331 and the narrowing portions 332 are alternately arranged, the width of the widening portion 331 is greater than the width of the narrowing portion 332, and the depth of the widening portion 331 is greater than the depth of the narrowing portion 332.

[0147] In some embodiments, the electrode sheet 30 is a negative electrode sheet of the electrode assembly 12 , the current collector is a negative electrode current collector, and the active material layer is a negative electrode active material layer.

[0148] In some embodiments, the electrode sheet is a positive electrode sheet of a battery cell, the current collector is a positive electrode current collector, and the active material layer is a positive electrode active material layer.

[0149] Along the thickness direction Z of the current collector 31, the current collector 31 has a first surface and a second surface opposite to each other, and the active material layer 32 may be provided on both the first surface and the second surface, or one of the first surfaces may be provided with the active material layer 32, and the other may not be provided with the active material layer 32. In the embodiment where the active material layer 32 is provided on both the first surface and the second surface, the groove 33 may be provided on the active material layer 32 on the first surface, the groove 33 may be provided on the active material layer 32 on the second surface, or the groove 33 may be provided on both the active material layer 32 on the first surface and the active material layer 32 on the second surface.

[0150] The groove 33 can be understood as a concave structure formed by removing part of the material on the surface of the active material layer 32. The groove 33 increases the surface area of ​​the active material layer 32 and enhances the capillary action of the active material layer 32. The pole piece 30 is used in the battery cell 10, the contact area between the active material layer 32 and the electrolyte is increased, and the wettability of the electrolyte is improved.

[0151] The extending direction of the groove 33 can be various. For example, the pole piece 30 is rectangular. In the embodiment where the pole piece 30 is rectangular, the extending direction of the groove 33 can be parallel to the length direction X of the current collector 31, and the extending direction of the groove 33 can also be parallel to the width direction Y of the current collector 31 (such as Fig. 9 and Fig.10 As shown in FIG. 1 ), the extension direction of the groove 33 may also be a direction that forms an angle with the width direction Y of the current collector 31 (as shown in FIG. 1 ). Figure 5 As shown in the figure), the extension direction of the groove 33 can also be a direction that forms an angle with the length direction X of the current collector 31.

[0152] It should be noted that the pole pieces 30 mentioned below refer to the pole pieces after being unfolded.

[0153] The widened portion 331 is the portion where the width of the groove 33 is widened, and the narrowed portion 332 is the portion where the width of the groove 33 is narrowed. The widened portion 331 has a larger cross-sectional area, and the narrowed portion 332 has a smaller cross-sectional area. In some embodiments, the widened portion 331 is the portion where the width of the groove 33 is the largest. In some embodiments, the narrowed portion 332 is the portion where the width of the groove 33 is the narrowest.

[0154] The widening structure between two adjacent narrowing portions 332 can be understood as a liquid reservoir, and the widest position of the liquid reservoir is the widening portion 331. On the projection plane perpendicular to the thickness direction Z of the current collector 31, the shape of the orthographic projection of the liquid reservoir can be various, and the orthographic projection of the liquid reservoir can be a rectangle (such as Fig. 9 as shown), round, spindle-shaped (as Figure 5 as shown) or irregular shapes, etc.

[0155] The widening portion 331 and the narrowing portion 332 are alternately arranged, which means that along the extension direction of the groove 33, the widening portion 331 and the narrowing portion 332 appear alternately, thereby forming a plurality of smaller liquid storage tanks. The ends of the groove 33 may be the widening portion 331 or the narrowing portion 332, or one end of the groove 33 may be the narrowing portion 332 and the other end may be the widening portion 331. For example, Figure 5 As shown, the end of the groove 33 is a narrowing portion 332. For example, Fig. 9 As shown, the end of the groove 33 is a widened portion 331 .

[0156] The width of the widened portion 331 is greater than the width of the narrowed portion 332, and the depth of the widened portion 331 is greater than the depth of the narrowed portion 332. It can be understood that the groove 33 is wider and deeper in the widened portion 331, and the cross-sectional area of ​​the widened portion 331 is larger, and the groove 33 is narrower and shallower in the narrowed portion 332, and the cross-sectional area of ​​the narrowed portion 332 is smaller.

[0157] The groove 33 can be formed in various ways. The groove 33 can be formed by laser etching on the surface of the active material layer 32, and the groove 33 can be formed on the surface of the active material layer 32 by mechanical processing, such as cutting. It should be noted that since the electrolyte is a liquid, the electrolyte tends to minimize the surface area, and the liquid tends to remain in the small groove. The electrolyte will be pulled to the edge of the small groove due to capillary action, which helps to keep the liquid in the groove. Therefore, a plurality of widening portions 331 and narrowing portions 332 are alternately arranged, so that the groove 33 forms a plurality of smaller liquid storage tanks. Compared with the grooves 33 of equal width, the liquid storage tanks are smaller, which is conducive to storing electrolyte and reducing the loss of electrolyte in the active material layer 32.

[0158] In the above technical solution, the groove 33 includes a plurality of widened portions 331 and a plurality of narrowed portions 332. The widened portions 331 and the narrowed portions 332 are alternately arranged along the extension direction of the groove 33. The width of the widened portion 331 is greater than the width of the narrowed portion 332. The depth of the widened portion 331 is greater than the depth of the narrowed portion 332. The widened portion 331 can be understood as the position where the width and depth of the groove 33 are expanded, and the narrowed portion 332 can be understood as the position where the width and depth of the groove 33 are narrowed. By forming grooves 33 on the surface of the active material layer 32, the pole piece 30 is used in the battery cell 10. Since multiple widened portions 331 and multiple narrowed portions 332 are alternately arranged, the widened portions 331 are convenient for storing electrolyte, and the electrolyte can be stored more between two adjacent narrowed portions 332, so that the electrolyte can infiltrate more into the deep position of the active material layer 32, thereby improving the lithium ion transmission rate in the deep position of the active material layer 32 and the current density in the deep position of the active material layer 32, thereby improving the charge and discharge rate and cycle life of the battery cell 10.

[0159] When the maximum width of the groove 33 is constant, compared with the groove 33 with a constant width (equal width), the groove 33 includes a plurality of widened portions 331 and a plurality of narrowed portions 332 . Along the extension direction of the groove 33 , the widened portions 331 and the narrowed portions 332 are alternately arranged, which can reduce the removal amount of the active material layer 32 .

[0160] Reference Figure 5 and Figure 6 In some embodiments, the width of the groove 33 gradually decreases from the widened portion 331 to the narrowed portion 332 .

[0161] It can be understood that the width of the groove 33 changes smoothly from the widening portion 331 to the narrowing portion 332 , and there is a smooth transition from the widening portion 331 to the narrowing portion 332 , and there is no step change in the width of the groove 33 from the widening portion 331 to the narrowing portion 332 .

[0162] In the above technical solution, the width of the groove 33 is gradually reduced from the widened portion 331 to the narrowed portion 332, so that a smooth transition is made between the width of the widened portion 331 and the width of the narrowed portion 332. There is no step between the widened portion 331 and the narrowed portion 332, which is beneficial to alleviate stress concentration and reduce the risk of the active material layer 32 falling off.

[0163] Reference Figure 6 and Fig. 9 In some embodiments, the width of the widened portion 331 is W1, satisfying 10 μm≤W1≤200 μm.

[0164] In the embodiment where the orthographic projection of the liquid storage tank is spindle-shaped on the projection plane perpendicular to the thickness direction Z of the current collector 31 , the width of the spindle at the maximum position can be understood as the width W1 of the widened portion 331 .

[0165] In an embodiment where the orthographic projection of the liquid storage tank is a rectangle on a projection plane perpendicular to the thickness direction Z of the current collector 31 , the width of the maximum position of the rectangle can be understood as the width W1 of the widened portion 331 .

[0166] Exemplarily, W1 can be 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 110μm, 120μm, 130μm, 140μm, 150μm, 160μm, 170μm, 180μm, 190μm, 200μm and any value therebetween.

[0167] In the above technical solution, W1≥10μm, the widened portion 331 will not be too wide, the groove 33 has a high capillary action ability, and the infiltration ability of the electrolyte along the extension direction of the groove 33 is improved, especially when the battery cell 10 is placed vertically, the infiltration along the top of the groove 33 is improved. W1≤200μm, the groove 33 will not be too narrow, which is conducive to more electrolyte storage in the groove 33. Therefore, W1 is between 10μm and 200μm, which can take into account both the capillary action brought by the groove 33 and the ability of the groove 33 to store electrolyte.

[0168] In some embodiments, 90 μm≤W1≤120 μm.

[0169] Exemplarily, W1 may be 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, 115 μm, or 120 μm.

[0170] In the above technical solution, the capillary effect brought by the groove 33 and the ability of the groove 33 to store electrolyte can be further taken into account.

[0171] Reference Figure 6 and Fig. 9 In some embodiments, the width of the narrowed portion 332 is W2, satisfying 5 μm≤W2≤100 μm.

[0172] The minimum width of the portion connecting two adjacent liquid storage tanks can be understood as the width W2 of the narrowed portion 332 .

[0173] Illustratively, W2 may be 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, and any value therebetween.

[0174] In the above technical solution, W2≥5μm, the narrowing portion 332 is not too narrow, and the narrowing portion 332 has a small degree of inhibition on the capillary action of the electrolyte along the extension direction of the groove 33. W2≤100μm, the narrowing portion 332 is not too wide, and has a small effect on the storage of electrolyte in the widening portion 331. Therefore, 5μm≤W2≤100μm can take into account both the capillary action brought by the groove 33 and the ability of the groove 33 to store electrolyte.

[0175] In some embodiments, 30 μm≤W2≤90 μm.

[0176] Exemplarily, W2 may be 30 μm, 50 μm, 60 μm, 70 μm, 80 μm, or 90 μm.

[0177] In the above technical solution, the capillary effect brought by the groove 33 and the ability of the groove to store electrolyte can be further taken into account.

[0178] Reference Figure 8 In some embodiments, the depth of the groove 33 gradually decreases from the widened portion 331 to the narrowed portion 332 .

[0179] It can be understood that the depth of the groove 33 transitions smoothly from the widened portion 331 to the narrowed portion 332 , and there is no step between the widened portion 331 and the narrowed portion 332 .

[0180] In the above technical solution, the depth of the groove 33 is gradually reduced from the widened portion 331 to the narrowed portion 332, and a smooth transition is made between the depth of the widened portion 331 and the depth of the narrowed portion 332. There is no step between the widened portion 331 and the narrowed portion 332, which is beneficial to alleviate stress concentration and reduce the risk of the active material layer 32 falling off.

[0181] Reference Figure 8 In some embodiments, the depth of the widened portion 331 is H, satisfying 5 μm≤H≤300 μm.

[0182] Illustratively, H may be 5 μm, 20 μm, 40 μm, 50 μm, 130 μm, 170 μm, 200 μm, 220 μm, 250 μm, 270 μm, 290 μm, 300 μm, and any value therebetween.

[0183] In the above technical solution, when H≥5μm, the groove 33 will not be too shallow, which is conducive to storing more electrolyte in the groove 33. When H≤300μm, the groove 33 will not be too deep, so that when the groove 33 is formed on the surface of the active material layer 32 by the processing equipment, the risk of cutting through the active material layer 32 and damaging the current collector 31 due to processing errors can be reduced, thereby improving the quality of the pole piece 30. Therefore, the depth of the widened portion 331 is between 5μm and 300μm, which can take into account both the quality of the pole piece 30 and the ability of the groove 33 to store electrolyte.

[0184] In some embodiments, 10 μm ≤ H ≤ 20 μm.

[0185] Illustratively, H may be 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, and any value therebetween.

[0186] In the above technical solution, the quality of the electrode 30 and the ability of the groove 33 to store electrolyte can be further taken into consideration.

[0187] Reference Figure 6 , Figure 8 and Fig. 9 In some embodiments, the distance between two adjacent narrowing portions 332 is W3, satisfying 0.02 mm ≤ W3 ≤ 20 mm.

[0188] The length of a liquid storage tank along the extension direction of the groove 33 can be understood as the distance W3 between two adjacent narrowing portions 332 .

[0189] Exemplarily, W3 can be 0.02 mm, 1 mm, 3 mm, 5 mm, 8 mm, 19 mm, 13 mm, 15 mm, 17 mm, 19 mm, 20 mm, and any value therebetween.

[0190] In the above technical solution, W3≥0.02mm, the distance between two adjacent narrowing portions 332 is not too small, which is conducive to storing electrolyte. W3≤20mm, the distance between two adjacent narrowing portions 332 is not too large, so that each groove 33 can be provided with more widening portions 331 to store electrolyte. Therefore, the distance between two adjacent narrowing portions 332 is between 0.02mm and 20mm, which can take into account the ability of the groove 33 to store electrolyte and the total amount of electrolyte stored in the groove 33.

[0191] In some embodiments, 1 mm ≤ W3 ≤ 3 mm.

[0192] Illustratively, W3 may be 1 mm, 1.3, 1.5 mm, 1.7 mm, 1.9 mm, 2 mm, 2.1 mm, 2.3 mm, 2.5 mm, 2.7 mm, 2.9 mm, 3 mm, and any value therebetween.

[0193] In the above technical solution, the ability of the groove 33 to store electrolyte and the total amount of electrolyte stored in the groove 33 can be further taken into consideration.

[0194] Reference Figure 5 , Fig. 9 and Fig.10In some embodiments, the groove 33 extends along the first direction S1, and a plurality of grooves 33 are provided. The plurality of grooves 33 are arranged at intervals along the second direction S2. The first direction S1 intersects with the second direction S2, and the first direction S1 and the second direction S2 are both perpendicular to the thickness direction Z of the current collector 31.

[0195] In some embodiments, reference Fig. 9 and Fig.10 , the first direction S1 is parallel to the width direction Y of the current collector 31 .

[0196] In some embodiments, reference Figure 5 The first direction S1 is parallel to the width direction Y of the current collector 31 and forms an angle therewith.

[0197] The second direction S2 may be parallel to the length direction X of the current collector 31, or the second direction S2 may be at an angle to the length direction X of the current collector 31. Figure 5 , Fig. 9 and Fig.10 , the second direction S2 is parallel to the length direction X of the current collector 31 .

[0198] In the above technical solution, a plurality of grooves 33 are provided, which can greatly improve the charge and discharge rate and cycle life of the battery cell 10 .

[0199] Reference Figure 5 In some embodiments, along the third direction S3 , the distance between two adjacent grooves 33 is W4 , satisfying 0.02 mm ≤ W4 ≤ 10 mm, and the third direction S3 , the first direction S1 , and the thickness direction Z of the current collector 31 are perpendicular to each other.

[0200] The distance W4 between two adjacent grooves 33 refers to the shortest distance between the grooves 33 , and this distance is measured along a straight line perpendicular to the extending direction of the grooves 33 .

[0201] In some embodiments, reference Fig. 9 and Fig.10 , the third direction S3 is parallel to the length direction X of the current collector 31.

[0202] In one embodiment, referring to Figure 5 , the third direction S3 forms an angle with the length direction X of the current collector 31.

[0203] Exemplarily, W4 can be 0.02 mm, 0.1 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, and any value therebetween.

[0204] In the above technical solution, W4≥0.02mm, the distance between two adjacent grooves 33 will not be too small, the number of grooves 33 set per unit area will not be too many, and the loss of active material layer 32 caused by grooves 33 will not be too much, so the impact on the energy density of battery cell 10 is small. W4≤10mm The distance between two adjacent grooves 33 will not be too large, so a larger number of grooves 33 can be set to improve the wettability of electrolyte in active material layer 32, improve the charge and discharge rate and cycle life of battery cell 10. Therefore, the distance between two adjacent grooves 33 is between 0.02mm and 10mm, which can take into account the energy density of battery cell 10 as well as the charge and discharge rate and cycle life of battery cell 10.

[0205] In some embodiments, 1.5 mm ≤ W4 ≤ 5 mm.

[0206] Exemplarily, W4 can be 1.5 mm, 1.7 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, and any value therebetween.

[0207] In the above technical solution, the energy density of the battery cell 10 as well as the charge and discharge rate and cycle life of the battery cell 10 can be further taken into consideration.

[0208] Reference Fig. 9 and Fig.10 In some embodiments, the second direction S2 is the length direction X of the current collector 31 , and the first direction S1 is parallel to the width direction Y of the current collector 31 . It can be understood that the plurality of grooves 33 are arranged along the length direction X of the current collector 31 .

[0209] The extension direction of the groove 33 is parallel to the width direction Y of the current collector 31 , which facilitates the control of the size of the groove 33 and reduces the difficulty of preparing the pole piece 30 .

[0210] Reference Figure 5 In some embodiments, the second direction S2 is the length direction X of the current collector 31 , and the first direction S1 forms an angle with the width direction Y of the current collector 31 .

[0211] The extending direction of the groove 33 forms an angle with the width direction Y of the current collector 31 , and the groove 33 is arranged obliquely, allowing the dimension of the groove 33 along the extending direction to be longer.

[0212] Fig.11 Schematic diagram of the structure of the pole piece 30 of some other embodiments of the present application.

[0213] Reference Fig.11In some embodiments, along the width direction Y of the current collector 31 , the current collector 31 has a first edge 311 and a second edge 312 opposite to each other, and the groove 33 has a first end 333 close to the first edge 311 and a second end 334 close to the second edge 312 .

[0214] Reference Fig.11 In some embodiments, the first end 333 extends to the first edge 311 .

[0215] In the above technical solution, the first end 333 extends to the first edge 311 , which can improve the wettability of the electrolyte at the first edge 311 .

[0216] In some embodiments, the second end 334 extends to the second edge 312 .

[0217] In the above technical solution, the second end 334 extends to the second edge 312 , which can improve the wettability of the electrolyte at the second edge 312 .

[0218] Reference Figure 5 In some embodiments, along the width direction Y of the current collector 31 , the current collector 31 has a first edge 311 and a second edge 312 opposite to each other, and the groove 33 has a first end 333 close to the first edge 311 and a second end 334 close to the second edge 312 .

[0219] In some embodiments, the first end 333 is spaced apart from the first edge 311 .

[0220] The first end 333 of the groove 33 is spaced apart from the first edge 311 , so that when the groove 33 is formed on the surface of the active material layer 32 by processing equipment, the risk of damaging the collector 31 due to processing errors and the processing stroke exceeding the first edge 311 can be reduced, thereby improving the quality of the pole piece 30 .

[0221] In some embodiments, the second end 334 is spaced apart from the second edge 312 .

[0222] The second end 334 of the groove 33 is spaced apart from the second edge 312 , so that when the groove 33 is formed on the surface of the active material layer 32 by processing equipment, the risk of damaging the collector 31 due to processing errors and the processing stroke exceeding the second edge 312 can be reduced, thereby improving the quality of the pole piece 30 .

[0223] In some embodiments, along the width direction Y of the current collector 31 , the distance between the first end 333 and the first edge 311 is L1 , satisfying 0.5 mm≤L1≤3 mm.

[0224] Illustratively, L1 may be 0.5 mm, 0.7 mm, 1 mm, 1.2 mm, 1.4 mm, 1.5 mm, 1.7 mm, 1.9 mm, 2 mm, 2.3 mm, 2.5 mm, 2.9 mm, 3 mm, and any value therebetween.

[0225] L2≥0.5mm, the distance between the groove 33 and the first edge 311 will not be too close, so that when the groove 33 is formed on the surface of the active material layer 32 by the processing equipment, the risk of damaging the current collector 31 due to the processing error and the processing stroke exceeding the active material layer 32 can be reduced, and the quality of the pole piece 30 can be improved. L2≤3mm, the groove 33 is not too far from the first edge 311, which is conducive to the preparation of the groove 33 with a longer extension size, thereby improving the wettability of the electrolyte in the active material layer 32 and improving the charge and discharge rate and cycle life of the battery cell 10. Therefore, the distance between the first end 333 and the first edge 311 is between 0.5mm and 3mm, which can take into account the reliability of the battery cell 10 and the charge and discharge rate and cycle life of the battery cell 10.

[0226] In some embodiments, along the width direction Y of the current collector 31 , the distance between the second end 334 and the second edge 312 is L2 , satisfying 0.5 mm≤L2≤3 mm.

[0227] Illustratively, L2 can be 0.5 mm, 0.7 mm, 1 mm, 1.2 mm, 1.4 mm, 1.5 mm, 1.7 mm, 1.9 mm, 2 mm, 2.3 mm, 2.5 mm, 2.9 mm, 3 mm, and any value therebetween.

[0228] L3≥0.5mm, the distance between the groove 33 and the second edge 312 will not be too close, so that when the groove 33 is formed on the surface of the active material layer 32 by the processing equipment, the risk of damaging the current collector 31 due to the processing error and the processing stroke exceeding the active material layer 32 can be reduced, and the quality of the pole piece 30 can be improved. L2≤3mm, the distance between the groove 33 and the second edge 312 will not be too far, which is conducive to the preparation of the groove 33 with a longer extension size, thereby improving the wettability of the electrolyte in the active material layer 32 and improving the charge and discharge rate and cycle life of the battery cell 10. Therefore, the distance between the second end 334 and the second edge 312 is between 0.5mm and 3mm, which can take into account the reliability of the battery cell 10 and the charge and discharge rate and cycle life of the battery cell 10.

[0229] In some embodiments, 0.6 mm ≤ L1 ≤ 1.5 mm.

[0230] Illustratively, L1 may be 0.6 mm, 0.7 mm, 0.8 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, and any value therebetween.

[0231] In the above technical solution, 0.6 mm ≤ L1 ≤ 1.5 mm, which can further take into account the reliability of the battery cell 10 and the charge and discharge rate and cycle life of the battery cell 10 .

[0232] In some embodiments, 0.6 mm ≤ L2 ≤ 1.5 mm.

[0233] Illustratively, L2 may be 0.6 mm, 0.7 mm, 0.8 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, and any value therebetween.

[0234] In the above technical solution, 0.6 mm ≤ L2 ≤ 1.5 mm, which can further take into account the reliability of the battery cell 10 and the charge and discharge rate and cycle life of the battery cell 10 .

[0235] Therefore, in some embodiments, the pole piece 30 is a negative pole piece 30 .

[0236] The N / P ratio is the ratio of the capacity of the negative electrode sheet 30 (Negative) to the capacity of the positive electrode sheet 30 (Positive), and this ratio is also called "cell balance" (CB). The N / P ratio is an important indicator for measuring the matching of the positive and negative electrode capacities of the battery cell 10. In order to slow down the release of lithium, the N / P ratio is usually large so that the capacity of the active material layer 32 of the negative electrode sheet 30 is surplus relative to the capacity of the active material layer 32 of the positive electrode sheet 30.

[0237] Since the provision of the grooves 33 will lead to the capacity loss of the active material layer 32, the provision of the grooves 33 on the surface of the active material layer 32 of the positive electrode sheet 30 will directly lead to a reduction in the energy density of the battery cell 10. Compared with the positive electrode sheet 30, the provision of the grooves 33 on the surface of the active material layer 32 of the negative electrode sheet 30 can utilize the surplus portion of the negative electrode sheet 30 relative to the positive electrode sheet 30, thereby reducing the impact of the capacity loss of the active material layer 32 caused by the grooves 33 on the energy density of the battery cell 10.

[0238] In some embodiments, the grooves 33 are formed by laser etching.

[0239] Laser etching of the groove 33 can reduce the difficulty of forming the groove 33 and reduce the difficulty of preparing the pole piece 30 .

[0240] At the same time, laser processing has high efficiency and can improve the preparation efficiency of the pole piece 30 .

[0241] In some embodiments, the extending direction of the groove 33 is parallel to the gravity direction, which can improve the wettability of the electrolyte on the top of the battery cell 10 .

[0242] In some embodiments, the electrode assembly 12 is a wound structure.

[0243] Furthermore, the extending direction of the groove is parallel to the winding axis of the electrode assembly, so that the groove can improve the wettability of the electrolyte along the winding axis.

[0244] In some embodiments, the electrode assembly 12 is a laminated structure.

[0245] Furthermore, the width direction Y of the current collector is parallel to the gravity direction, the groove 33 extends along the gravity direction, and the electrode assembly further includes two pole tabs, which are arranged on the same side of the electrode assembly along the length direction X of the current collector 31 .

[0246] In other embodiments, the two tabs are respectively disposed on both sides of the electrode assembly along the length direction X of the current collector 31 .

[0247] An embodiment of the present application provides an electrical device, which includes the above-mentioned battery device 100, and the battery device 100 is used to provide electrical energy.

[0248] Fig.12 This is a schematic diagram of the structure of the laser device of some embodiments of the present application. The embodiments of the present application provide a laser device, which includes a laser, a reflector and a galvanometer. The laser is used to output laser light, and the laser irradiates the laser light to the reflector. The reflector changes the direction of the laser light by reflection so that the laser light irradiates in the direction of the pole piece. The galvanometer is arranged between the reflector and the pole piece, and the galvanometer is used to control the direction of the laser light, thereby controlling the moving trajectory (laser etching processing path) of the light spot formed by the laser light on the active material layer, thereby etching a groove on the surface of the active material layer.

[0249] Fig.13 Flow chart of a method for preparing a battery cell 10 according to some embodiments of the present application.

[0250] Reference Fig.13 , an embodiment of the present application provides a method for preparing a battery cell 10 , the method can be used to prepare the above-mentioned battery cell 10 , and the method can be applied to the above-mentioned laser device.

[0251] In some embodiments, the preparation method comprises:

[0252] S100, providing a pole piece 30, wherein the pole piece 30 includes a current collector 31 and an active material layer 32 disposed on at least one side of the current collector 31 in a thickness direction Z;

[0253] S200 , a continuous laser with periodically changing power is used to etch grooves 33 with alternating widths and depths on the surface of the active material layer 32 .

[0254] Continuous laser means that during the process of etching a groove 33 , continuous laser output is provided, and the laser works continuously and uninterruptedly on the surface of the active material layer 32 .

[0255] The power changes periodically, which means that the laser power changes back and forth within the range between the first power and the second power. After the laser power gradually changes from the first power to the second power, it continues to gradually change from the second power to the first power, which is a cycle, and so on. The first power is not equal to the second power.

[0256] The grooves 33 with alternating width and depth refer to that the groove depth is deeper in the wide part and shallower in the narrow part. The wide part can be understood as the widening part 331 and the narrowing part can be understood as the narrowing part 332. Multiple widening parts 331 and multiple narrowing parts 332 are alternately arranged.

[0257] It should be understood that the greater the laser power, the larger the spot formed by the laser on the active material layer, the greater the etching depth and etching width, and the smaller the laser power, the smaller the spot formed by the laser on the active material layer, the greater the etching depth and etching width. Therefore, during the operation of the spot along the etching path, the laser power is controlled to change periodically between the first power and the second power, and the spot size changes periodically accordingly, so that a groove with alternating width and depth can be obtained. The widening portion 331 is etched at the position with the maximum laser power, and the widening portion 331 is etched at the position with the minimum laser power.

[0258] In some embodiments, the time of each cycle may be equal, thereby obtaining a groove with uniformly varying width and depth.

[0259] In some embodiments, the first power is less than the second power, and the narrowing portion 332 is etched at the position of the first power, and the narrowing portion 332 is etched at the position of the second power. In one cycle, a liquid reservoir with narrow ends and wide middle can be etched, and multiple continuous liquid reservoirs can be etched by repeating multiple cycles. Multiple continuous liquid reservoirs are grooves.

[0260] Further, the laser is controlled to start from the first power, repeat multiple cycles, and then end at the first power, so that the groove 33 (such as Figure 5 As shown). Multiple cycles are repeated to obtain grooves 33 with alternating widths and narrownesses and alternating depths and shallownesses.

[0261] In some embodiments, reference Fig.12 The preparation method may include seven etching cycles, namely t1, t2, t3, t4, t5, t6, and t7. The time of each cycle may be equal.

[0262] Since the galvanometer can control the residence time of the laser on the active material layer 32, the slower the galvanometer vibrates, the longer the laser stays at the same position, the laser continues to work at one position, the active material layer absorbs more energy, and more material is etched. On the contrary, the faster the galvanometer vibrates, the laser quickly scans a certain position, the shorter the laser stays at the same position, the active material layer absorbs less energy, and less material is etched. Therefore, in some embodiments, the galvanometer movement frequency can be controlled to change periodically without changing the laser power, so as to obtain a groove 33 with alternating width and depth.

[0263] The galvanometer movement frequency changes periodically, which means that the galvanometer changes back and forth within the range between the first vibration frequency and the second vibration frequency. After the galvanometer movement frequency gradually changes from the first vibration frequency to the second vibration frequency, it continues to gradually change from the second vibration frequency to the first vibration frequency, which is one cycle, and so on. Among them, the first vibration frequency and the second vibration frequency. It should be understood that the greater the vibration frequency, the faster the movement speed of the light spot formed by the laser on the active material layer 32, and the smaller the vibration frequency, the slower the movement speed of the light spot formed by the laser on the active material layer 32.

[0264] In some embodiments, reference Fig.12 The preparation method may include seven etching cycles, in each etching cycle, after the vibration frequency of the galvanometer changes from the first vibration frequency to the second vibration frequency, it continues to change from the second vibration frequency to the first vibration frequency. Repeating multiple cycles can obtain a groove with uniformly varying width and depth.

[0265] In some embodiments, the first vibration frequency is less than the second vibration frequency, and the narrowed portion 332 may be etched at the first vibration frequency, and the widened portion 331 may be etched at the second vibration frequency.

[0266] In some embodiments, reference Figures 4 to 8, the embodiment of the present application provides a pole piece 30, and the pole piece 30 is a negative pole piece. The pole piece 30 includes a current collector 31 and an active material layer 32 arranged on at least one side of the thickness direction Z of the current collector 31. A plurality of grooves 33 are arranged on the surface of the active material layer 32 away from the current collector 31, and the plurality of grooves 33 are arranged along the length direction X of the current collector 31. The grooves 33 extend along a first direction S1, and the first direction S1 forms an angle with the width direction Y of the current collector 31. Along the width direction Y of the current collector 31. The current collector 31 has a first edge 311 and a second edge 312 opposite to each other, and the groove 33 has a first end 333 close to the first edge 311 and a second end 334 close to the second edge 312. The first end 333 is spaced apart from the first edge 311, and the second end 334 is spaced apart from the second edge 312. The groove 33 includes a plurality of narrowing portions 332 and a plurality of widening portions 331. Along the extension direction of the groove 33, the widening portions 331 and the narrowing portions 332 are alternately arranged. The width of the widening portion 331 is greater than the width of the narrowing portion 332, the depth of the widening portion 331 is greater than the depth of the narrowing portion 332, and the depth of the widening portion 331 is greater than the depth of the narrowing portion 332. From the widening portion 331 to the narrowing portion 332, the width of the groove 33 gradually decreases, and the depth of the groove 33 also gradually decreases. Along the extension direction of the groove 33, the groove 33 presents alternating changes in depth and shallowness accompanied by alternating changes in width and narrowness, and the cycle of alternating changes in depth and shallowness is the same as that of alternating changes in width and narrowness. The groove 33 forms a liquid storage tank between two adjacent narrowing portions 332, the widening portion 331 coincides with the deepest position of the liquid storage tank, and the widening portion 331 coincides with the widest position of the liquid storage tank. The bottom of the liquid storage tank is an arc surface. Each groove 33 is formed by continuous etching with periodically changing laser. The width of the widened portion 331 is between 90μm and 120μm, and the width of the narrowed portion 332 is between 5μm and 100μm. The depth of the widened portion 331 is between 10μm and 20μm. The distance between two adjacent narrowed portions 332 is between 1mm and 3mm. Along the third direction S3, the distance between two adjacent grooves 33 is between 1.5mm and 5mm. The third direction S3, the first direction S1 and the thickness direction Z of the current collector 31 are perpendicular to each other. Along the width direction Y of the current collector 31, the first end 333 to the first edge 311 is between 0.6mm and 1.5mm, and the second end 334 to the hot edge is between 0.6mm and 1.5mm.

[0267] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0268] The above embodiments are only used to illustrate the technical solution of the present application and are not used to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A battery cell, characterized in that: include: An electrode assembly, the electrode assembly comprising a pole piece, the pole piece comprising a current collector and an active material layer disposed on at least one side of the current collector in a thickness direction, wherein a surface of the active material layer facing away from the current collector is provided with a groove; Wherein, the groove includes multiple widening parts and multiple narrowing parts. Along the extension direction of the groove, the widening parts and the narrowing parts are alternately arranged, the width of the widening part is greater than the width of the narrowing part, and the depth of the widening part is greater than the depth of the narrowing part.

2. The battery cell according to claim 1, characterized in that: The width of the groove gradually decreases from the widened portion to the narrowed portion.

3. The battery cell according to claim 1, characterized in that: The width of the widened portion is W1, which satisfies 10 μm≤W1≤200 μm.

4. The battery cell according to claim 3, characterized in that: 90μm≤W1≤120μm.

5. The battery cell according to claim 1, characterized in that: The width of the narrowed portion is W2, satisfying 5μm≤W2≤100μm.

6. The battery cell according to claim 5, characterized in that: 30μm≤W2≤90μm.

7. The battery cell according to claim 1, characterized in that: The depth of the groove gradually decreases from the widened portion to the narrowed portion.

8. The battery cell according to claim 1, characterized in that: The depth of the widened portion is H, which satisfies 5 μm≤H≤300 μm.

9. The battery cell according to claim 8, characterized in that: 10μm≤H≤20μm.

10. The battery cell according to claim 1, characterized in that: The distance between two adjacent narrowing portions is W3, which satisfies 0.02mm≤W3≤20mm.

11. The battery cell according to claim 10, characterized in that: 1mm≤W3≤3mm.

12. The battery cell according to any one of claims 1 to 11, characterized in that: The groove extends along a first direction, a plurality of the grooves are provided, and the plurality of the grooves are arranged at intervals along a second direction, the first direction intersects with the second direction, and the first direction and the second direction are both perpendicular to the thickness direction of the current collector.

13. The battery cell according to claim 12, characterized in that: Along the third direction, the distance between two adjacent grooves is W4, satisfying 0.02 mm ≤ W4 ≤ 10 mm, and the third direction, the first direction and the thickness direction of the current collector are perpendicular to each other.

14. The battery cell according to claim 13, characterized in that: 1.5mm≤W4≤5mm.

15. The battery cell according to claim 12, characterized in that: The second direction is the length direction of the current collector, and the first direction is parallel to or forms an angle with the width direction of the current collector.

16. The battery cell according to claim 15, characterized in that: Along the width direction of the current collector, the current collector has a first edge and a second edge opposite to each other, and the groove has a first end close to the first edge and a second end close to the second edge; wherein the first end extends to the first edge; and / or, The second end extends to the second edge.

17. The battery cell according to claim 15, characterized in that: Along the width direction of the current collector, the current collector has a first edge and a second edge opposite to each other, and the groove has a first end close to the first edge and a second end close to the second edge; wherein the first end is spaced apart from the first edge; and / or, The second end is spaced apart from the second edge.

18. The battery cell according to claim 17, characterized in that: Along the width direction of the current collector, the distance between the first end and the first edge is L1, satisfying 0.5 mm ≤ L1 ≤ 3 mm; and / or, Along the width direction of the current collector, a distance between the second end and the second edge is L2, satisfying 0.5 mm ≤ L2 ≤ 3 mm.

19. The battery cell according to claim 18, characterized in that: 0.6mm≤L1≤1.5mm; and / or, 0.6mm≤L2≤1.5mm.

20. The battery cell according to any one of claims 1 to 11, characterized in that: The pole piece is the negative pole piece of the electrode assembly.

21. The battery cell according to any one of claims 1 to 11, characterized in that: The grooves are formed by laser etching.

22. The battery cell according to any one of claims 1 to 11, characterized in that: The electrode assembly is a wound structure or a laminated structure.

23. A battery device, characterized in that: A battery cell comprising the battery cell according to any one of claims 1 to 22.

24. An electrical device, characterized in that: The battery device according to claim 23 is used to provide electrical energy.

25. A method for preparing a battery monomer, characterized in that ,include: Providing a pole piece, the pole piece comprising a current collector and an active material layer disposed on at least one side of the current collector in a thickness direction; A continuous laser with periodically changing power is used to etch grooves with alternating widths and depths on the surface of the active material layer.

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